• Structural Engineering and Mechanics
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• 제54권3호
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• pp.419-432
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• 2015

The free vibration of rotating Euler-Bernoulli beams with the thickness and/or width of the cross-section vary linearly along the length is investigated by using the Adomian modified decomposition method (AMDM). Based on the AMDM, the governing differential equation for the rotating tapered beam becomes a recursive algebraic equation. By using the boundary condition equations, the dimensionless natural frequencies and the closed form series solution of the corresponding mode shapes can be easily obtained simultaneously. The computed results for different taper ratios as well as different offset length and rotational speeds are presented in several tables and figures. The accuracy is assured from the convergence and comparison with the previous published results. It is shown that the AMDM provides an accurate and straightforward method of free vibration analysis of rotating tapered beams.

• 한국전산구조공학회논문집
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• 제25권3호
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• pp.185-194
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• 2012

이 연구는 회전관성과 전단변형을 동시에 고려한 변단면 Timoshenko 보의 자유진동에 관한 연구이다. 변단면 보의 단면은 폭이 포물선 함수로 변화하는 변화폭 직사각형 단면으로 채택하였다. 이러한 보의 자유진동을 지배하는 수직변위에 대한 4계 상미분방정식을 유도하였다. 이 상미분방정식을 수치해석하여 고유진동수와 진동형을 산출하였다. 수치해석 예에서는 회전-회전, 회전-고정, 고정-고정 지점을 고려하였다. 진동형은 변위의 진동형뿐만 아니라 합응력의 진동형도 산출하여 그림에 나타내었다. 휨 회전각과 전단변형에 의한 수직변위 및 전단면 회전각의 구성비율을 산정하였다.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2000년도 봄 학술발표회논문집
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• pp.92-99
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• 2000

The nondimensional differential equations governing the buckling loads of tapered columns with both clamped ends and its boundary conditions are derived, in which the effects of shear deformations are included. These equations are solved numerically using a numerical integration technique and a bracketing method to obtain the buckling loads of columns. Four types of cross-sectional shape are considered in the numerical examples. The parametric studies of shear deformation effects on the buckling loads such as cross-sectional shape factor, shear coefficient, ratio of modulus of elasticity, slenderness ratio and section ratio are reported in tables and figures.

• 한국농공학회지
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• 제36권4호
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• pp.56-63
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• 1994

The nondimensional differential equations governing the buckling loads of tapered columns and its houndarv conditions are derived, in which the effects of shear deformations are included. These equations are solved numerically using a numerical integration technique and a bracketing method to obtain the buckling loads of columns. Four types of cross-sectional shape with clamped-free end constraint are used in the numerical examples. The parametric studies of shear deformation effects on the buckling loads such as cross-sectional shape factor, shear coefficient, ratio of modulus of elasticity, slenderness ratio and section ratio are reported in tables and figures.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2012년도 추계학술대회 논문집
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• pp.75-80
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• 2012

Helmholtz resonator is widely used acoustic instrument which has high absorption characteristics at its resonance frequency. Particularly it maintains good performance even in the low frequency region that is difficult to control by general porous absorptive materials. However, under severely high sound pressure level, the absorption characteristics are changed by increase of resistance due to nonlinear behavior of neck impedance. Because of this nonlinear behavior, it is difficult to obtain the expected absorption performance under high sound pressure environment. Thus, in order to prevent excessive rise of resistance, the resonator with neck having cross section dimension decrease away from the entry of the resonator cavity could be suggested. This paper introduces the experiment method and results about nonlinear characteristics of Helmholtz resonator with tapered neck and proposes the approximate nonlinear impedance model.

• Structural Engineering and Mechanics
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• 제9권6호
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• pp.569-588
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• 2000

The plastic collapse loads and their locations are predicted for a class of tapered, initially curved, and transversely corrugated cantilevered beams subjected to static tip loading. Results of both closed form and finite element solutions for several rigid perfectly plastic and elastic perfectly plastic beam models are evaluated. The governing equations are cast in nondimensional form for efficient studies of collapse load as it varies with beam geometry and the angle of the tip load. Static experiments for laboratory-scale configurations whose taper flared toward the tip, complemented the theory in that collapse occurred at points about 40% of the beams length from the fixed end. Experiments for low speed impact loading of these configurations showed that collapse occurred further from the fixed end, between the 61% and 71% points. The results may be applied to the design of safer highway guardrail terminal systems that collapse by design under vehicle impact.

• Structural Engineering and Mechanics
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• 제59권2호
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• pp.243-259
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• 2016

This research develops a finite element code for the transient dynamic analysis of tapered fiber reinforced polymer (FRP) poles with hollow circular cross-section and flexible joints used in power transmission lines. The FRP poles are modeled by tapered beam elements and their flexible joints by a rotational spring. To solve the time equations of transient dynamic analysis, precise time integration method is utilized. In order to verify the utilized formulations, a typical jointed FRP pole under step, triangular and sine pulses is analyzed by the developed finite element code and also ANSYS commercial finite element software for comparison. Thereafter, the effect of joint flexibility on its dynamic behavior is investigated. It is observed that by increasing the joint stiffness, the amplitude of the pole tip deflection history decreases, and the time of occurrence of the maximum deflection is earlier.

• 한국방재학회 논문집
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• 제8권2호
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• pp.45-49
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• 2008

본 논문에서는 미국 AISC-LRFD기준에서 제시하고 있는 웨브 변단면 I형 보의 탄성 좌굴강도 산정식을 고찰하였다. 미국 AISC-LRFD 기준의 기본 개념은 웨브 변단면 보를 가장 작은 단면과 동일한 크기를 가지면서 길이가 다른 등가 일정단면보로 대치하는 것이다. 또한 비지지 구간에 작용하는 응력 구배와 이웃한 보의 횡방향 구속효과를 고려하기 위하여 수정계수(B)를 적용하고 있다. AISC-LRFD 기준에 제시된 수정계수(B)와 유한요소해석결과와의 비교를 통해 본 논문에서는 수정계수(B)를 산정하기 위한 재 정의된 방법을 제안하였다.

• 복합신소재구조학회 논문집
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• 제6권3호
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• pp.77-85
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• 2015

In this paper, we present the result of investigations pertaining to the elastic buckling of simply supported columns with various cross-sectional dimensions but the same length and volume. In the investigations the accuracy of the analysis methods is studied and it was found that the result obtained by the successive approximations technique is the most accurate. In addition, the elastic buckling loads of columns with variable cross-section dimensions are obtained by the theoretical and numerical methods. From the results, it was found that the buckling loads obtained by the numerical methods are close to the buckling loads obtained by the successive approximations technique for the practical standpoints. Moreover, the buckling load of column with convexity in its middle is the highest while the buckling load of the tapered column is the lowest as expected.

• Steel and Composite Structures
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• 제4권4호
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• pp.281-301
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• 2004

The paper begins by presenting a unified variational approach to the lateral-torsional buckling (LTB) analysis of doubly symmetric prismatic and tapered thin-walled beams with open cross-sections, which accounts for the influence of the pre-buckling deflections. This approach (i) extends the kinematical assumptions usually adopted for prismatic beams, (ii) consistently uses shell membrane theory in general coordinates and (iii) adopts Trefftz's criterion to perform the bifurcation analysis. The proposed formulation is then applied to investigate the influence of the pre-buckling deflections on the LTB behaviour of prismatic and web-tapered I-section simply supported beams and cantilevers. After establishing an interesting analytical result, valid for prismatic members with shear centre loading, several elastic critical moments/loads are presented, discussed and, when possible, also compared with values reported in the literature. These numerical results, which are obtained by means of the Rayleigh-Ritz method, (i) highlight the qualitative differences existing between the LTB behaviours of simply supported beams and cantilevers and (ii) illustrate how the influence of the pre-buckling deflections on LTB is affected by a number of factors, namely ($ii_1$) the minor-to-major inertia ratio, ($ii_2$) the beam length, ($ii_3$) the location of the load point of application and ($ii_4$) the bending moment diagram shape.